Not Applicable
Stents, grafts, stent-grafts, vena cava filters and similar implantable medical devices, collectively referred to hereinafter as stents, are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. Stents may be implanted in a variety of body lumens or vessels such as within the vascular system, urinary tracts, bile ducts, etc. Stents may be used to reinforce body vessels and to prevent restenosis following angioplasty in the vascular system. They may be self-expanding or expanded by an internal radial force, such as when mounted on a balloon.
Stents are generally tubular devices for insertion into body lumens. Balloon expandable stents require mounting over a balloon, positioning, and inflation of the balloon to expand the stent radially outward. Self-expanding stents expand into place when unconstrained, without requiring assistance from a balloon. A self-expanding stent is biased so as to expand upon release from the delivery catheter. Some stents may be characterized as hybrid stents which have some characteristics of both self-expandable and balloon expandable stents.
A vessel having a stenosis may be viewed as an inwardly protruding arcuate addition of hardened material to a cylindrical vessel wall, where the stenosed region presents a somewhat rigid body attached along, and to, the elastic wall. The stenosis presents resistance to any expansion of the vessel in the region bridged by the stenosis. Stenoses vary in composition, for example, in the degree of calcification, and therefore vary in properties as well.
A stent may be used to provide a prosthetic intraluminal wall e.g. in the case of a stenosis to provide an unobstructed conduit for blood in the area of the stenosis. An endoluminal prosthesis comprises a stent which carries a prosthetic graft layer of fabric and is used e.g. to treat an aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of embolism, or of the natural artery wall bursting. Typically, a stent or endoluminal prosthesis is implanted in a blood vessel at the site of a stenosis or aneurysm by so-called xe2x80x9cminimally invasive techniquesxe2x80x9d in which the stent is compressed radially inwards and is delivered by a catheter to the site where it is required through the patient""s skin or by a xe2x80x9ccut downxe2x80x9d technique in which the blood vessel concerned is exposed by minor surgical means. When the stent is positioned at the correct location, the catheter is withdrawn and the stent is caused or allowed to re-expand to a predetermined diameter in the vessel.
U.S. Pat. No. 4,886,062 discloses a vascular stent which comprises a length of sinuous or xe2x80x9czig-zagxe2x80x9d wire formed into a helix; the helix defines a generally cylindrical wall which, in use, constitutes a prosthetic intraluminal wall. The sinuous configuration of the wire permits radial expansion and compression of the stent; U.S. Pat. No. 4,886,062 discloses that the stent can be delivered percutaneously and expanded in situ using a balloon catheter.
U.S. Pat. No. 4,733,665 discloses an expandable intraluminal graft which is constituted by a tubular member formed from a plurality of intersecting elongate members which permit radial expansion and compression of the stent.
EP-A-0556850 discloses an intraluminal stent which is constituted by a sinuous wire formed into a helix; juxtaposed apices of the wire are secured to one another so that each hoop of the helix is supported by its neighboring hoops to increase the overall strength of the stent and to minimize the risk of plaque herniation; in some embodiments the stent of EP-A-0556850 further comprises a tubular graft member to form an endoluminal prosthesis.
The devices cited above are generally satisfactory for the treatment of aneurysms, stenoses and other angeological diseases at sites in continuous unbifurcated portions of arteries or veins.
Within the vasculature however it is not uncommon for stenoses to form at a vessel bifurcation. A bifurcation is an area of the vasculature or other portion of the body where a first (or parent) vessel is bifurcated into two or more branch vessels. Where a stenotic lesion or lesions form at such a bifurcation, the lesion(s) can affect only one of the vessels (i.e., either of the branch vessels or the parent vessel) two of the vessels, or all three vessels. Many prior art stents however are not wholly satisfactory for use where the site of desired application of the stent is juxtaposed or extends across a bifurcation in an artery or vein such, for example, as the bifurcation in the mammalian aortic artery into the common iliac arteries.
For example, in the case of an abdominal aortic aneurysm (xe2x80x9cAAAxe2x80x9d) in the infrarenal portion of the aorta which extends into one of the common iliac arteries, the use of one of the prior art prosthesis referred to above across the bifurcation into the one iliac artery will result in obstruction of the proximal end of the other common iliac artery; by-pass surgery is therefore required to connect the one iliac artery in juxtaposition with the distal end of the prosthesis to the other blocked iliac artery. It will be appreciated by a person skilled in the art that it is desirable to avoid surgery wherever possible; the requirement for by-pass surgery associated with the use of the prior art prosthesis in juxtaposition with a bifurcation in an artery therefore constitutes a significant disadvantage.
Another example of a vessel bifurcation is the left and right common carotid arteries. These arteries are the principal arteries of the head and neck. Both of the common carotid arteries are quite similar and divide at a carotid bifurcation or bulb into an external carotid artery and an internal carotid artery. In the region of the carotid bulb and the ostium of the internal carotid artery, stenoses present a particular problem for carotid stenting due to the large tapering of the vessel interior from the common carotid artery (both the left and the right) to the internal carotid artery. The region of the carotid bifurcation or bulb happens to be where stenoses most often occur, particularly in the region of the ostium to the internal carotid artery in both of the carotid arteries.
Embodiments of the present invention relate to endoluminal prosthesis (stents) that may be utilized in the region of a bifurcation of vessels. The present invention also embraces stent connecting means for connecting a stent (e.g. a stent which forms part of an endoluminal prosthesis or bifurcated stent) to another stent or portion thereof. Some embodiments of the invention are directed to designs of bifurcated stents and their method of manufacture, as well as apparatuses and methods for introducing prostheses to the vasculature and methods of treating angeological diseases.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.
The present invention includes many different embodiments. At least one embodiment of the invention is directed to bifurcated stents and the methods of treating stenoses at a bifurcation site.
In some embodiments of the invention, the bifurcated stent includes at least one coiled member that defines at least one branch of the stent. In some embodiments the stent is characterized as having an expanding coil geometry. The expanding coil geometry provides at least one branch coil of the bifurcated stent with a larger diameter and/or a tighter coil pitch. In some embodiments of the invention, the portion of the stent that is deployed into the main branch includes a coil pitch that is greater than the pitch of adjacent stent coils. The at least one coiled member may be characterized as wire, ribbon or a combination thereof. Preferably, the wire coil will have an elliptical or round cross-section, whereas a ribbon may be characterized as a flattened wire coil. The wire ribbon or coil may be constructed from an etched panel of stent material or be manufactured from laser cut tubing.
In some embodiments where the coil is constructed from at least one ribbon, the ribbon may define a loose pitch coil or a tight pitch coil. In embodiments where the ribbon defines a tight pitch coil, the ribbon is preferably constructed of Nitinol and/or Elgiloy. In embodiments where the ribbon defines a coil, the coil may have a substantially helical configuration.
In some embodiments of the invention a stent may be a generally tubular body having one more openings with at least one coiled member engaged thereto. The coiled member may define at least one branch of the bifurcated stent. The coiled portion and the generally tubular body may have similar or different physical and/or performance characteristics. For example, the generally tubular body may define a balloon expandable primary portion of the bifurcated stent, whereas the coiled portion may define a self-expandable branch of the bifurcated stent that extends from the primary portion subsequent to expansion of the primary portion.
In at least one embodiment, the coiled portion has a collapsed state and a delivered state. In the collapsed state the coiled portion is collapsed in upon itself within the plane of the tubular wall the primary portion. In the delivered state, the coiled portion extends outwardly from the primary portion to a predetermined length.
In at least one embodiment of the invention a bifurcated stent comprises a primary portion having at least one branch portion. The branch portion is a woven mesh defined by at least one wire. The primary portion defines at least one opening through which the branch portion may be passed and engaged thereto. The branch portion is delivered through the primary portion in a collapsed inverted state and is expanded to a delivered state extending from the primary portion and in fluid communication therewith. Preferably, the woven mesh of the branch portion is constructed from Nitinol wire. In at least one embodiment, an end of the branch portion is welded to the area of the primary portion that defines the opening. Alternatively the wire of the branch portion is threaded through one or more flanges of the primary portion.
In at least one embodiment of the invention, the bifurcated stent includes one or more wire members which define a loop or loops within the interior of the primary section immediately adjacent to the opening through which a branch portion extends from. The loops preferably have a radius which is larger than the opening. The end of the branch portion immediately adjacent to the primary portion is engaged to one or more of the loops.
In at least one embodiment of the invention a bifurcated stent comprises a generally tubular primary portion which defines at least one side opening and two longitudinal openings. The bifurcated stent further comprises at least one coiled member which defines one or more side branches. Preferably, the at least one coiled member extends through the primary portion to provide a first coiled branch portion extending from the at least one side opening and a second coiled branch portion extending from at least one of the longitudinal openings. Preferably, the at least one coiled member is a wire and/or ribbon of Nitinol.
Additional details and/or embodiments of the invention are discussed below.